Processes and compositions for the reduction of nitrogen oxides in an effluent from the combustion of a carbonaceous fuel have been developed extensively over recent years. With the increased attention to the health risks and environmental damage caused by agents such as smog and acid rain, it is expected that NO.sub.x reduction research will continue to be pursued.
In the past, most processes for the reduction of nitrogen oxides levels have concentrated on achieving maximum NO.sub.x reductions without addressing the problems raised by the production of other pollutants such as ammonia and carbon monoxide. More recently, in a unique application of NO.sub.x -reducing principles, Epperly, Peter-Hoblyn, Shulof, Jr. and Sullivan, in U.S. Pat. No. 4,777,024, disclosed a method of achieving substantial nitrogen oxides reductions while minimizing the production of other pollutants through a multiple stage injection process. Moreover, Epperly, O'Leary, and Sullivan, in U.S. Pat. No. 4,780,289, have disclosed a complementary process for achieving significant, and potentially maximized, NO.sub.x reductions while minimizing the production of other pollutants by utilizing the nitrogen oxides reduction versus effluent temperature curve of the treatment regimen being effected at each NO.sub.x reduction introduction in a combustion system. These inventions, though, focused mainly on minimizing the levels of ammonia and carbon monoxide, and do not address the generation of N.sub.2 O.
What is desired, therefore, is a system whereby nitrogen oxides reductions can be achieved without the generation of substantial amounts of nitrous oxide. Preferably, such system also leads to the minimization of the production of other pollutants.